@fourotwo/types

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|__/     \______/  \______/ |__/       \______/    \___/   \_____/\___/  \______/ 
                                                                                      

Shared types, DID derivation, and the x402 payment-envelope codec for fourotwo.

The single source of truth for the shapes and byte formats used across the fourotwo facilitator, registry, SDK, and dashboard. Because every component imports the same package, DIDs and signed payloads are byte-identical everywhere ensuring no drift between signer and verifier.

Most agent developers use @fourotwo/agent-sdk and never import this directly. Reach for it when you build a server that accepts payments, or need DID/envelope primitives on their own.

Install

npm install @fourotwo/types

DID derivation

A fourotwo agent DID is did:fourotwo:{network}:{address}, derived deterministically from a public key (Casper → blake2b account hash, Base → EVM address).

import { deriveDid, deriveAddress, parseDid } from '@fourotwo/types';

const did = deriveDid('casper', publicKeyHex);
// did:fourotwo:casper:3d5de8c609159a0954e773dd686fb7724428316cb30e00bdc...

const { network, address } = parseDid(did);

Payment envelope codec

The PAYMENT-REQUIRED envelope a server sends on a 402, and the canonical bytes that get signed. Use encodeEnvelope when issuing a 402; the signer and verifier both sign canonicalPaymentBytes so signatures always line up.

import { encodeEnvelope, decodeEnvelope, canonicalPaymentBytes } from '@fourotwo/types';

const header = encodeEnvelope({
  amount: '5000',                 // smallest unit (motes / wei)
  recipient: 'account-hash-...',
  network: 'casper',
  token: 'CSPR',
  expiry: Math.floor(Date.now() / 1000) + 600,
  nonce: 'unique-per-request',    // replay protection
  facilitator: 'https://fourotwo-facilitator.onrender.com',
  minTrustScore: 40,              // optional gating
});

res.writeHead(402, { 'PAYMENT-REQUIRED': header });

What's exported

• DID / addresses — deriveDid, deriveAddress, formatDid, parseDid, isValidDid, casperAccountHash, baseAddress, DID_METHOD
• Envelope codec — encodeEnvelope, decodeEnvelope, canonicalPaymentBytes, canonicalPaymentMessage
• Trust helpers — tierForScore, TIER_COLOR
• Types — PaymentRequired, PaymentPayload, VerifyRequest, VerifyResponse, SettleRequest, SettleResponse, SettlementReceipt, SupportedResponse, TrustScore, TrustTier, TrustDimensions, ChainNetwork, SettlementMode, and more.

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